No doubt about that, the line was the US didnt want to give them missiles that they can fire into Crimea so not to provoke a Russian response. There's been UK Storm Shadows and French SCALP missiles raining down on Crimea, I havent seen London or Paris being hit in response.
The reason for the US hesitation is far more likely that Russian (and therefore China) radars will be able to track ATACMS flight paths, even though they are randomised in the last few mins) and potentially workout a defence against them down the line.
The reason for the hesitation in the US supplying ATACMS is that Ukraine specifically requested the M57 (500lb) GPS guided warhead version.
The US needs to maintain its own stock of this variant as it waits for the PrSM to come on-line (this is the replacement for ATACMS).
They also have to satisfy existing export orders of the M57 and can only produce 500 per year apparently.
They do have a shed load of M39/M39A1 warheads (cluster bomblets), so these are the ones that will probably be shipped to Ukraine.
Either way the HIMARS/M270 launch platforms will require a software/firmware upgrade in order to support ATACMS.